In Escherichia coli B/r, the size of the cells appears to be determined by the number and the degree of overlapping of envelope synthetic sequences initiated at a discrete number of loci at the time of inauguration of new rounds of DNA replication. The aim of this study is the elucidation of the interrelation between envelope synthesis and DNA replication. The extent of the coupling between the two sequences will be determined by analyzing the effect of inhibition of envelope and DNA synthesis on cell growth and division. The proposed work include 1) analysis of cell sizes during a nutritional shiftup and during inhibition of synthesis of protein, DNA and elements of envelope, 2) analysis of cell sizes during a nutritional shiftdown, 3) pattern of incorporation of DNA and envelope precursors during nutritional shifts and during inhibition of macromolecular synthesis, 4) pattern of segregation of envelope elements. The studies will be performed on cells of a given age and possessing known chromosomal configuration. BIBLIOGRAPHIC REFERENCES: O. Pierucci and C.E. Helmstetter. Chromosome Segregation in Escherichia coli B/r at Various Growth Rates. J. Bacteriol., 1976, in press. C.E. Helmstetter and O. Pierucci. DNA Synthesis during the Division Cycle of Three Substrains of Escherichia coli B/r. J. Mol. Biol. 102, 477-486, 1976.